A standard blister pack is typically made by feeding a flat cover foil and a blister foil having preferably filled blisters to the nip between a sealing roll and a blister roll. The sealing roll is oriented above the pocket roll and has a smooth and cylindrical outer surface. The pocket roll has a cylindrical outer surface formed with an array of pockets spaced to fit complementary with the filled pockets of the blister foil, which is fed horizontally to the nip with its blisters open upward. The cover foil and blister foil are pressed together so that they fuse where the seal-roll outer surface presses the foils together against the lands between the pockets of the blister roll.
Since it is absolutely critical that the blisters be perfectly centered in the pockets of the pocket roll, a system is provided for detecting and adjusting the position of the blister foil in the tangential feed direction. This means includes a sensor that detects the positions of the pockets and that is coupled to the drive for the pocket roll so that it can determine when the blisters are drifting from on-center positions.
In DE 10 2004 010 202 of J. Riekenbrauck such a device is described that provides for the continuous sealing of the blister foil with strict correlation of the blisters in the blister foil with the pockets in the surface of the pocket roll. For this purpose, the device has a two-part pocket roll whose effective diameter can be varied slightly so as to compensate for nonalignment of the blisters with the pockets of the pocket roll. This device has proven of value in practice regarding the application for which the device is designed. It is, however, not possible to process blister foil displacement beyond about 1% with this device.